1. Field of the Invention
The present invention relates to an ice making machine and, in particular, to an improved ice making machine in which the freezing capacity of a freezing circuit is adjusted by detecting the ice making capacity of the ice making machine, thereby controlling the ice making capacity.
2. Description of the Related Art
Generally speaking, in an auger type ice making machine, its ice making mechanism comprises a drive motor (geared motor), a housing, a freezing casing, an auger (screw), etc., and ice making water supplied from a water supply tank to a cylinder contained in the freezing casing is stored while maintaining a fixed water level, ice being made continuously during operation of the ice making mechanism. Refrigerant flows through an evaporator, and ice gradually grows on the inner wall surface of the ice making cylinder. This ice is scraped off by a screw rotated by the geared motor, conveyed upwards, and cut into small pieces by a cutter (hereinafter also referred to as a stationary blade). The freezing circuit comprises an electric compressor, a condenser, a dehydrator, a thermal expansion valve, an evaporator, etc., and contains refrigerant therein. In the condenser, refrigerant at high temperature is cooled by a condenser cooling fan and is liquefied.
Ice made by an auger type ice making machine is often used in an ice bed or the like for cooling drinks, foods, etc. in a fast-food restaurant; the amount of ice used is maximum in the summer, when the atmospheric temperature is high. Naturally, the ice making machine is designed such that its cooling capacity satisfies demands corresponding to high temperature.
Thus, the refrigerant gas is cooled efficiently or inefficiently according to changes in the atmospheric temperature and water temperature, thereby indicating the capacity of the machine.
However, as can be seen from the capacity chart of FIG. 31, in a conventional apparatus, the ice making capacity gradually deteriorates as the temperature and water temperature increase; depending upon the condition for the design spec capacity, the spec capacity varies under different conditions.
Since the design spec capacity is adjusted to high temperature, the freezing capacity becomes too large under low temperature environment, with the result that the cylinder is clogged with ice, with an excessive load being applied to the screw. This leads to problems, such as generation of unusual noise and breakage of the drive motor.
In view of this, Japanese Patent Laid Open No. 06-207768, Japanese Patent Laid Open No. 08-178487, Japanese Utility Model Laid Open No. 59-47172, and Japanese Patent Laid Open No. 57-142466 disclose a technique according to which the temperatures of the condenser and the evaporator are measured, and the RPM (revolutions per minute) of the drive motor is varied according to the measurements to thereby avoid the above problem. Apart from this, Japanese Patent Laid Open Nos. 61-125566 and 09-303914 disclose a technique according to which the ice making capacity is controlled according to variation in a detected current value; the detection of a current value, however, is subject to the influence of fluctuations in voltage. Further, the difference between normal and abnormal current values is rather small, so that it is extremely difficult to recognize.
Therefore, although both the above conventional techniques help to avoid breakage and failure of the drive motor, they have a problem in that an excessive amount of ice is likely to be made, resulting in large consumption of electric power and water and a rather short service life.
This invention has been made with a view toward solving the above problems in the prior art. It is an object of this invention to provide an ice making machine whose ice making capacity is optimally controlled according to the environment in which ice making operation is performed, whereby an excess in ice making capacity is eliminated, thereby achieving a reduction in the consumption of electric power and water and preventing failure and breakage of the ice making mechanism portion so as to achieve an increase in service life.
In accordance with this invention, there is provided an ice making machine comprising: an ice making portion; a water supply tank for supplying ice making water to the ice making portion; a freezing circuit including an evaporator for cooling ice making water supplied to the ice making portion to make ice; ice making capacity detecting means for detecting fluctuation in ice making capacity; and a control circuit which adjusts the freezing capacity of the freezing circuit whenever fluctuation in ice making capacity is detected by the ice making capacity detecting means.
The ice making capacity detecting means can be constructed such that it detects fluctuation in ice making capacity by comparing one of the following factors with the corresponding reference values:
(1) an ice making water consumption time;
(2) a temperature of the condenser of the freezing circuit;
(3) a compression ratio of the compressor of the freezing circuit;
(4) an ice making water consumption time and a temperature of the condenser of the freezing circuit;
(5) an ice making water consumption time and a compression ratio of the compressor of the freezing circuit;
(6) an ice making water consumption time, a temperature of the condenser of the freezing circuit and a compression ratio of the compressor of the freezing circuit;
(7) an evaporation temperature of the refrigerant of the evaporator of the freezing circuit;
(8) a flow rate of the ice making water supplied to the ice making portion; and
(9) change in the level of the ice making water in the water supply tank.
In a case that one of the temperature of the condenser, the compression ratio of the compressor and the evaporation temperature of the refrigerant of the evaporator is compared with the corresponding reference value, the reference value may be adjusted based on the atmospheric temperature or the temperature of the ice making water.
It is desirable for the control circuit to be constructed so as to adjust the RPM of the fan motor of the condenser of the freezing circuit or the RPM of the compressor of the freezing circuit.